As conventional technologies for realizing path operation, there are MPLS (refer to non-patent document 1), GMPLS (refer to non-patent document 2 or 3), and the like. Path establishment function for these techniques, that is, signaling techniques are realized by using RSVP-TE (Resource Reservation Protocol for Traffic Engineering) which is a signaling protocol (refer to non-patent document 3 or 4).
In the signaling technique such as the RSVP-TE, a numeric value relating to path setup priority is provided to individual paths, and a function is provided in which a path having high priority reuses resources of a path of low priority.
In the standard specification of RSVP-TE, two values that are holding priority and set-up priority are defined as priority information of path establishment, and a function is provided in which, when setup priority of a path to be newly established is higher than holding priority of an already established path, reuse of resources occur, and the originally established path is deleted.
There are following documents as related art documents,                [Non-patent document 1] IETF RFC3031        [Non-patent document 2] IETF RFC3471        [Non-patent document 3] IETF RFC3473        [Non-patent document 4] IETF RFC3209        [Non-patent document 5] IETF RFC3630        [Non-patent document 6] IETF RFC3292        [Patent document 1] Japanese Laid-Open Patent Application No. 2005-269377        [Patent document 2] Japanese Laid-Open Patent Application No. 2003-229902        [Patent document 3] Japanese Laid-Open Patent Application No. 4-256246        